Analysis of compaction in the preimplantation mouse embryo
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Abstract:
An SEM analysis of the effects of tunicamycin, cytochalasin B, and colcemid has yielded insights into the process of compaction in the early mouse embryo. All three reagents block or reverse compaction and decrease the number of microvilli (MV), although some MV polarization is permitted. In addition, tunicamycin is shown to lessen cell adhesion even in compacted embryos. Cytochalasin B causes the formation of MV clumps some of which are preferentially localized to the apex or lateral ring region. Colcemid reverses compaction and, coupled with Pronase treatment, completely blocks compaction of uncompacted 8-cell embryos. Observations also suggest that MV polarization can occur only once but compaction (the close adherance and flattening of blastomeres) can be reversed and reinduced. Evidence is consistent with a three-step compaction process involving (1) cell surface recognition and attachment of a ring of lateral microvilli to adjacent blastomeres, (2) subsequent microfilament shortening in these lateral MV, and (3) maintenance of the compacted and polarized state by microtubules.
Insights
Tunicamycin, cytochalasin B, and colcemid disrupt early mouse embryo compaction by affecting microvilli (MV) and cell adhesion. These findings reveal a three-step process essential for blastomere flattening and cell attachment.
Area of Science:
- Developmental Biology
- Cell Biology
Background:
- Early embryonic development involves critical processes like compaction.
- Understanding compaction mechanisms is key to developmental biology.
Purpose of the Study:
- To investigate the effects of specific reagents on early mouse embryo compaction.
- To elucidate the molecular mechanisms underlying blastomere adhesion and flattening.
Main Methods:
- Scanning Electron Microscopy (SEM) analysis.
- Treatment of early mouse embryos with tunicamycin, cytochalasin B, and colcemid.
Main Results:
- Tunicamycin, cytochalasin B, and colcemid inhibit or reverse embryo compaction.
- These reagents reduce microvilli (MV) number and alter their distribution.
- Tunicamycin decreases cell adhesion, while cytochalasin B forms MV clumps.
Conclusions:
- Compaction is a dynamic process involving cell surface interactions, microfilament activity, and microtubule-dependent maintenance.
- Microvilli polarization appears to be a unidirectional event, while compaction is reversible.